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<a href="sobel_8cl.html">Go to the documentation of this file.</a><div class="fragment"><div class="line"><a name="l00001"></a><span class="lineno">    1</span>&#160;<span class="comment">/*</span></div>
<div class="line"><a name="l00002"></a><span class="lineno">    2</span>&#160;<span class="comment"> * This confidential and proprietary software may be used only as</span></div>
<div class="line"><a name="l00003"></a><span class="lineno">    3</span>&#160;<span class="comment"> * authorised by a licensing agreement from ARM Limited</span></div>
<div class="line"><a name="l00004"></a><span class="lineno">    4</span>&#160;<span class="comment"> *    (C) COPYRIGHT 2013 ARM Limited</span></div>
<div class="line"><a name="l00005"></a><span class="lineno">    5</span>&#160;<span class="comment"> *        ALL RIGHTS RESERVED</span></div>
<div class="line"><a name="l00006"></a><span class="lineno">    6</span>&#160;<span class="comment"> * The entire notice above must be reproduced on all authorised</span></div>
<div class="line"><a name="l00007"></a><span class="lineno">    7</span>&#160;<span class="comment"> * copies and copies may only be made to the extent permitted</span></div>
<div class="line"><a name="l00008"></a><span class="lineno">    8</span>&#160;<span class="comment"> * by a licensing agreement from ARM Limited.</span></div>
<div class="line"><a name="l00009"></a><span class="lineno">    9</span>&#160;<span class="comment"> */</span></div>
<div class="line"><a name="l00010"></a><span class="lineno">   10</span>&#160;</div>
<div class="line"><a name="l00018"></a><span class="lineno"><a class="code" href="sobel_8cl.html#ad999d1681236d38b8c3e05c610a99850">   18</a></span>&#160;__kernel <span class="keywordtype">void</span> <a class="code" href="sobel_8cl.html#ad999d1681236d38b8c3e05c610a99850" title="Sobel filter kernel function.">sobel</a>(__global <span class="keyword">const</span> uchar* restrict inputImage,</div>
<div class="line"><a name="l00019"></a><span class="lineno">   19</span>&#160;                    <span class="keyword">const</span> <span class="keywordtype">int</span> width,</div>
<div class="line"><a name="l00020"></a><span class="lineno">   20</span>&#160;                    __global <span class="keywordtype">char</span>* restrict outputImageDX,</div>
<div class="line"><a name="l00021"></a><span class="lineno">   21</span>&#160;                    __global <span class="keywordtype">char</span>* restrict outputImageDY)</div>
<div class="line"><a name="l00022"></a><span class="lineno">   22</span>&#160;{</div>
<div class="line"><a name="l00023"></a><span class="lineno">   23</span>&#160;    <span class="comment">/* [Kernel size] */</span></div>
<div class="line"><a name="l00024"></a><span class="lineno">   24</span>&#160;    <span class="comment">/*</span></div>
<div class="line"><a name="l00025"></a><span class="lineno">   25</span>&#160;<span class="comment">     * Each kernel calculates 16 output pixels in the same row (hence the &#39;* 16&#39;).</span></div>
<div class="line"><a name="l00026"></a><span class="lineno">   26</span>&#160;<span class="comment">     * column is in the range [0, width] in steps of 16.</span></div>
<div class="line"><a name="l00027"></a><span class="lineno">   27</span>&#160;<span class="comment">     * row is in the range [0, height].</span></div>
<div class="line"><a name="l00028"></a><span class="lineno">   28</span>&#160;<span class="comment">     */</span></div>
<div class="line"><a name="l00029"></a><span class="lineno">   29</span>&#160;    <span class="keyword">const</span> <span class="keywordtype">int</span> column = get_global_id(0) * 16;</div>
<div class="line"><a name="l00030"></a><span class="lineno">   30</span>&#160;    <span class="keyword">const</span> <span class="keywordtype">int</span> row = get_global_id(1) * 1;</div>
<div class="line"><a name="l00031"></a><span class="lineno">   31</span>&#160;</div>
<div class="line"><a name="l00032"></a><span class="lineno">   32</span>&#160;    <span class="comment">/* Offset calculates the position in the linear data for the row and the column. */</span></div>
<div class="line"><a name="l00033"></a><span class="lineno">   33</span>&#160;    <span class="keyword">const</span> <span class="keywordtype">int</span> offset = row * width + column;</div>
<div class="line"><a name="l00034"></a><span class="lineno">   34</span>&#160;    <span class="comment">/* [Kernel size] */</span></div>
<div class="line"><a name="l00035"></a><span class="lineno">   35</span>&#160;</div>
<div class="line"><a name="l00036"></a><span class="lineno">   36</span>&#160;    <span class="comment">/* [Load row] */</span></div>
<div class="line"><a name="l00037"></a><span class="lineno">   37</span>&#160;    <span class="comment">/*</span></div>
<div class="line"><a name="l00038"></a><span class="lineno">   38</span>&#160;<span class="comment">     * First row of input.</span></div>
<div class="line"><a name="l00039"></a><span class="lineno">   39</span>&#160;<span class="comment">     * In a scalar Sobel calculation you would load 1 value for leftLoad, middleLoad and rightLoad.</span></div>
<div class="line"><a name="l00040"></a><span class="lineno">   40</span>&#160;<span class="comment">     * In the vector case we load 16 values for each.</span></div>
<div class="line"><a name="l00041"></a><span class="lineno">   41</span>&#160;<span class="comment">     * leftLoad, middleLoad and rightLoad load 16-bytes of data from the first row.</span></div>
<div class="line"><a name="l00042"></a><span class="lineno">   42</span>&#160;<span class="comment">     * The data they load overlaps. e.g. for the first column and row, leftLoad is 0-&gt;15, middleLoad is 1-&gt;16 and rightLoad is 2-&gt;17.</span></div>
<div class="line"><a name="l00043"></a><span class="lineno">   43</span>&#160;<span class="comment">     * So we&#39;re actually loading 18-bytes of data from the first row.</span></div>
<div class="line"><a name="l00044"></a><span class="lineno">   44</span>&#160;<span class="comment">     */</span></div>
<div class="line"><a name="l00045"></a><span class="lineno">   45</span>&#160;    uchar16 leftLoad = vload16(0, inputImage + (offset + 0));</div>
<div class="line"><a name="l00046"></a><span class="lineno">   46</span>&#160;    uchar16 middleLoad = vload16(0, inputImage + (offset + 1));</div>
<div class="line"><a name="l00047"></a><span class="lineno">   47</span>&#160;    uchar16 rightLoad = vload16(0, inputImage + (offset + 2));</div>
<div class="line"><a name="l00048"></a><span class="lineno">   48</span>&#160;    <span class="comment">/* [Load row] */</span></div>
<div class="line"><a name="l00049"></a><span class="lineno">   49</span>&#160;</div>
<div class="line"><a name="l00050"></a><span class="lineno">   50</span>&#160;    <span class="comment">/* [Convert data] */</span></div>
<div class="line"><a name="l00051"></a><span class="lineno">   51</span>&#160;    <span class="comment">/*</span></div>
<div class="line"><a name="l00052"></a><span class="lineno">   52</span>&#160;<span class="comment">     * Convert the data from unsigned chars to shorts (8-bit unsigned to 16-bit signed).</span></div>
<div class="line"><a name="l00053"></a><span class="lineno">   53</span>&#160;<span class="comment">     * The calculations can overflow 8-bits so we require larger intermediate storage.</span></div>
<div class="line"><a name="l00054"></a><span class="lineno">   54</span>&#160;<span class="comment">     * Additionally, the values can become negative so we need a signed type.</span></div>
<div class="line"><a name="l00055"></a><span class="lineno">   55</span>&#160;<span class="comment">     */</span></div>
<div class="line"><a name="l00056"></a><span class="lineno">   56</span>&#160;    short16 leftData = convert_short16(leftLoad);</div>
<div class="line"><a name="l00057"></a><span class="lineno">   57</span>&#160;    short16 middleData = convert_short16(middleLoad);</div>
<div class="line"><a name="l00058"></a><span class="lineno">   58</span>&#160;    short16 rightData = convert_short16(rightLoad);</div>
<div class="line"><a name="l00059"></a><span class="lineno">   59</span>&#160;    <span class="comment">/* [Convert data] */</span></div>
<div class="line"><a name="l00060"></a><span class="lineno">   60</span>&#160;</div>
<div class="line"><a name="l00061"></a><span class="lineno">   61</span>&#160;    <span class="comment">/* [Calculation] */</span></div>
<div class="line"><a name="l00062"></a><span class="lineno">   62</span>&#160;    <span class="comment">/*</span></div>
<div class="line"><a name="l00063"></a><span class="lineno">   63</span>&#160;<span class="comment">     * Calculate the results for the first row.</span></div>
<div class="line"><a name="l00064"></a><span class="lineno">   64</span>&#160;<span class="comment">     * Looking at the Sobel masks above for the first line of input,</span></div>
<div class="line"><a name="l00065"></a><span class="lineno">   65</span>&#160;<span class="comment">     * the dX calculation is the sum of 1 * leftData, 0 * middleData, and -1 * rightData.</span></div>
<div class="line"><a name="l00066"></a><span class="lineno">   66</span>&#160;<span class="comment">     * The dY calculation is the sum of 1 * leftData, 2 * middleData, and 1 * rightData.</span></div>
<div class="line"><a name="l00067"></a><span class="lineno">   67</span>&#160;<span class="comment">     * This is what is being calculated below, except we have removed the</span></div>
<div class="line"><a name="l00068"></a><span class="lineno">   68</span>&#160;<span class="comment">     * unnecessary calculations (multiplications by 1 or 0) and we are calculating 16 values at once.</span></div>
<div class="line"><a name="l00069"></a><span class="lineno">   69</span>&#160;<span class="comment">     * This pattern repeats for the other 2 rows of data.</span></div>
<div class="line"><a name="l00070"></a><span class="lineno">   70</span>&#160;<span class="comment">     */</span></div>
<div class="line"><a name="l00071"></a><span class="lineno">   71</span>&#160;    short16 dx = rightData - leftData;</div>
<div class="line"><a name="l00072"></a><span class="lineno">   72</span>&#160;    short16 dy = rightData + leftData + middleData * (short)2;</div>
<div class="line"><a name="l00073"></a><span class="lineno">   73</span>&#160;    <span class="comment">/* [Calculation] */</span></div>
<div class="line"><a name="l00074"></a><span class="lineno">   74</span>&#160;</div>
<div class="line"><a name="l00075"></a><span class="lineno">   75</span>&#160;    <span class="comment">/*</span></div>
<div class="line"><a name="l00076"></a><span class="lineno">   76</span>&#160;<span class="comment">     * Second row of input.</span></div>
<div class="line"><a name="l00077"></a><span class="lineno">   77</span>&#160;<span class="comment">     * By adding the &#39;width * 1&#39; to the offset we get the next row of data at the same column position.</span></div>
<div class="line"><a name="l00078"></a><span class="lineno">   78</span>&#160;<span class="comment">     * middleData is not loaded because it is not used in any of the calculations.</span></div>
<div class="line"><a name="l00079"></a><span class="lineno">   79</span>&#160;<span class="comment">     */</span></div>
<div class="line"><a name="l00080"></a><span class="lineno">   80</span>&#160;    leftLoad = vload16(0, inputImage + (offset + width * 1 + 0));</div>
<div class="line"><a name="l00081"></a><span class="lineno">   81</span>&#160;    rightLoad = vload16(0, inputImage + (offset + width * 1 + 2));</div>
<div class="line"><a name="l00082"></a><span class="lineno">   82</span>&#160;</div>
<div class="line"><a name="l00083"></a><span class="lineno">   83</span>&#160;    leftData = convert_short16(leftLoad);</div>
<div class="line"><a name="l00084"></a><span class="lineno">   84</span>&#160;    rightData = convert_short16(rightLoad);</div>
<div class="line"><a name="l00085"></a><span class="lineno">   85</span>&#160;</div>
<div class="line"><a name="l00086"></a><span class="lineno">   86</span>&#160;    <span class="comment">/*</span></div>
<div class="line"><a name="l00087"></a><span class="lineno">   87</span>&#160;<span class="comment">     * Calculate the results for the second row.</span></div>
<div class="line"><a name="l00088"></a><span class="lineno">   88</span>&#160;<span class="comment">     * The dX calculation is the sum of -2 * leftData, 0 * middleData, and -2 * rightData.</span></div>
<div class="line"><a name="l00089"></a><span class="lineno">   89</span>&#160;<span class="comment">     * There is no dY calculation to do: sum of 0 * leftData, 0 * middleData, and 0 * rightData.</span></div>
<div class="line"><a name="l00090"></a><span class="lineno">   90</span>&#160;<span class="comment">     */</span></div>
<div class="line"><a name="l00091"></a><span class="lineno">   91</span>&#160;    dx += (rightData - leftData) * (<span class="keywordtype">short</span>)2;</div>
<div class="line"><a name="l00092"></a><span class="lineno">   92</span>&#160;</div>
<div class="line"><a name="l00093"></a><span class="lineno">   93</span>&#160;    <span class="comment">/* Third row of input. */</span></div>
<div class="line"><a name="l00094"></a><span class="lineno">   94</span>&#160;    leftLoad = vload16(0, inputImage + (offset + width * 2 + 0));</div>
<div class="line"><a name="l00095"></a><span class="lineno">   95</span>&#160;    middleLoad = vload16(0, inputImage + (offset + width * 2 + 1));</div>
<div class="line"><a name="l00096"></a><span class="lineno">   96</span>&#160;    rightLoad = vload16(0, inputImage + (offset + width * 2 + 2));</div>
<div class="line"><a name="l00097"></a><span class="lineno">   97</span>&#160;</div>
<div class="line"><a name="l00098"></a><span class="lineno">   98</span>&#160;    leftData = convert_short16(leftLoad);</div>
<div class="line"><a name="l00099"></a><span class="lineno">   99</span>&#160;    middleData = convert_short16(middleLoad);</div>
<div class="line"><a name="l00100"></a><span class="lineno">  100</span>&#160;    rightData = convert_short16(rightLoad);</div>
<div class="line"><a name="l00101"></a><span class="lineno">  101</span>&#160;</div>
<div class="line"><a name="l00102"></a><span class="lineno">  102</span>&#160;    <span class="comment">/*</span></div>
<div class="line"><a name="l00103"></a><span class="lineno">  103</span>&#160;<span class="comment">     * Calculate the results for the third row.</span></div>
<div class="line"><a name="l00104"></a><span class="lineno">  104</span>&#160;<span class="comment">     * The dX calculation is the sum of -1 * leftData, 0 * middleData, and -1 * rightData.</span></div>
<div class="line"><a name="l00105"></a><span class="lineno">  105</span>&#160;<span class="comment">     * The dY calculation is the sum of -1 * leftData, -2 * middleData, and -1 * rightData.</span></div>
<div class="line"><a name="l00106"></a><span class="lineno">  106</span>&#160;<span class="comment">     */</span></div>
<div class="line"><a name="l00107"></a><span class="lineno">  107</span>&#160;    dx += rightData - leftData;</div>
<div class="line"><a name="l00108"></a><span class="lineno">  108</span>&#160;    dy -= rightData + leftData + middleData * (short)2;</div>
<div class="line"><a name="l00109"></a><span class="lineno">  109</span>&#160;</div>
<div class="line"><a name="l00110"></a><span class="lineno">  110</span>&#160;    <span class="comment">/* [Store] */</span></div>
<div class="line"><a name="l00111"></a><span class="lineno">  111</span>&#160;    <span class="comment">/*</span></div>
<div class="line"><a name="l00112"></a><span class="lineno">  112</span>&#160;<span class="comment">     * Store the results.</span></div>
<div class="line"><a name="l00113"></a><span class="lineno">  113</span>&#160;<span class="comment">     * The range of outputs from our Sobel calculations is [-1020, 1020].</span></div>
<div class="line"><a name="l00114"></a><span class="lineno">  114</span>&#160;<span class="comment">     * In order to output this as an 8-bit signed char we must divide it by 8 (or shift right 3 times).</span></div>
<div class="line"><a name="l00115"></a><span class="lineno">  115</span>&#160;<span class="comment">     * This gives the range [-128, 128]. Depending on what type of output you require,</span></div>
<div class="line"><a name="l00116"></a><span class="lineno">  116</span>&#160;<span class="comment">     * (signed/unsigned, seperate/combined gradients) it is possible to do more of the calculations on the GPU using OpenCL.</span></div>
<div class="line"><a name="l00117"></a><span class="lineno">  117</span>&#160;<span class="comment">     * In this sample we&#39;re assuming that the application requires signed uncombined gradient outputs.</span></div>
<div class="line"><a name="l00118"></a><span class="lineno">  118</span>&#160;<span class="comment">     */</span></div>
<div class="line"><a name="l00119"></a><span class="lineno">  119</span>&#160;    vstore16(convert_char16(dx &gt;&gt; 3), 0, outputImageDX + offset + width + 1);</div>
<div class="line"><a name="l00120"></a><span class="lineno">  120</span>&#160;    vstore16(convert_char16(dy &gt;&gt; 3), 0, outputImageDY + offset + width + 1);</div>
<div class="line"><a name="l00121"></a><span class="lineno">  121</span>&#160;    <span class="comment">/* [Store] */</span></div>
<div class="line"><a name="l00122"></a><span class="lineno">  122</span>&#160;}</div>
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